Composition for a desulfurizer with a high sulfur capacity and the process of making the same

ABSTRACT

The present invention discloses a composition for a desulfurizer with a high sulfur capacity and a process for making the same. The composition comprises the active components of three kinds of iron oxides and is used in the desulfurizer to remove hydrogen sulfide from the gaseous and liquid state feed stocks. The above-mentioned composition comprises cubic ferroferric oxide in the form of crystalline phase (Fe 3 O 4 ), amorphous ferric oxide (Fe 2 O 3 ) and amorphous ferric oxide monohydrate (Fe 2 O 3 .H 2 O). The composition has a sulfur capacity of at least 40%. The process for preparing the composition comprises the following steps: (1) mixing a solid ferrous compound with a solid hydroxide at a molar ratio of iron to hydroxyl being in the range from 1:2 to 1:3; (2) kneading the mixture feeds obtained in step (1) and making them react completely; (3) drying the products obtained in step (2) in the air; (4) washing and filtering the feeds obtained in the step (3); (5) naturally drying or baking the solids obtained in step (4) to form a composition for a desulfurizer with a high sulfur capacity. The process of the present invention is simple and easy to operate, consumes less energy and produces the products with a stable quality.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a composition for a desulfurizer with a highsulfur capacity and a process of making the same. More specifically,this invention relates to iron oxides as the active components of thecomposition for a desulfurizer with a high sulfur capacity and thepreparation process thereof. Said iron oxides are particularly suitableto serve as the desulfurizer's active components to remove the hydrogensulfide presents in gaseous and liquid state feed stocks.

BACKGROUND ART

The presence of hydrogen sulfide (H₂S) in the course of manufacturingchemical materials from coal or petroleum will poison and thusdeactivate catalysts used in the subsequent processing stages. A largeamount of industrial waste water or waste gases also containconsiderable hydrogen sulfide (H₂S) and other sulfides, which willpollute the environment or poison humans or animals if directly emitted.Presently, desulfurizer are usually used in the desulfurization ofhydrogen sulfide (H₂S)-containing gases such as coal gas, hydrogen,synthetic gas, ammonia gas and gaseous hydrocarbon etc., or hydrogensulfide-containing liquid hydrocarbons, such as kerosene, gasoline andcyclohexane etc. There are many kinds of desulfurizers, and iron oxideis one conventional desulfurizer. The disadvantages of this kind ofdesulfurizers are that they can be applied to a narrow range oftemperature and air velocity, have a low reactive efficiency and sulfurcapacity, and generally can only be employed in the primary crudedesulfurization or in combination with other kinds of desulfurizers.

At present, the active components of most iron oxide desulfurizersinclude other metal oxides besides iron oxides. For example, ChinesePatent Application-CN1287875A discloses a compositionM_(x)O_(y).Fe₂O₃.nH₂O comprising ferric oxide monohydrate and one ormore other metal compounds, wherein the metal is selected from the groupconsisting of Ti, Co, Ni, Mo, Zn, Cd, Cr, Hg, Cu, Ag, Sn, Pb and Bi,and/or alkaline-earth metals such as Ca, Mg. Chinese PatentApplication-CN1121950A discloses a desulfurizer with crude iron ore,scoria and zinc oxide serving as raw material. Chinese PatentApplication-CN1068356A discloses a desulfurizer with iron-mud waste,sintered zinc ferrite as raw material. There are also desulfurizersusing crude iron-containing minerals as raw material. For example,Chinese Patent Application-CN1121950A discloses a desulfurizercomprising crude iron ore, scoria and zinc oxide, and Chinese PatentApplication-CN1368537A discloses a desulfurizer comprising ore rich iniron, lignite and a small quantity of calcareousness, wherein the orerich in iron can be hematite. Japanese Patent Application No. JP59039345discloses a desulfurizer comprising 40 to 90% iron oxide (such ashematite), titanium dioxide and silicon dioxide. Although the costs ofsaid desulfurizer are low, it is difficult to keep the active componentsof the desulfurizer stable because the components of the raw materialare variable.

Additionally, ferrite is used as the raw material to preparedesulfurizers with a wet method. For example, Chinese PatentApplication-CN1312132A discloses a desulfurizer prepared by reactingferrous sulphate solution, ammonia as precipitator, calcareousness,sodium carbonate, and a small quantity of metal oxides. Severalside-reactions will take place during the precipitation when the ferricsalt solution precipitation method is used to form the iron oxides, andit is difficult to control these side-reactions by adjusting the pHvalue. Thus, it is difficult to control the final composition of theactive components, which makes the sulfur capacity uncontrollable.

Additionally, there are also a kind of desulfurizers containing iron oriron oxide as sole active component. For example, Chinese PatentApplication-CN1539545 discloses a desulfurizer comprising 15 to 80% ironoxide and Direct Reduced Iron (spongy iron); U.S. Pat. No. 5,102,636discloses a desulfurizer comprising 5 to 95% iron oxide and 95 to 5%iron complex. This kind of desulfurizers sufficiently take advantage ofthe desulfurizing function of the iron, however, the cost is relativelyhigh.

Chinese Patent Application-CN 1395994A discloses a process for preparingan iron additive used in iron-alkali desulfurizing catalyst, wherein aferrous sulfate (or ferrous chloride) solution and a sodium carbonate(or sodium hydroxide) solution are mixed to cause precipitation reactionto form said iron additive. This reaction in the solution is apt toobtaining colloid which is uneasy to be washed.

It is well known that the performance of a desulfurizer primarilydepends on factors, such as sulfur capacity, desulfurizing precision andtemperature. The higher the sulfur capacity and the desulfurizingprecision, the better the performance of the desulfurizer becomes.However, the sulfur capacity of the present iron oxide desulfurizers isless than 40%.

DETAILED DESCRIPTION OF THE INVENTION

The first object of the present invention is to provide a compositionfor a desulfurizer capable of removing H₂S present in gaseous or liquidstate feed stocks without the control of the temperature and pressure.

The second object of the present invention is to provide a process forpreparing said composition for a desulfurizer with a high sulfurcapacity. The process is simple and easy to operate, consumes lessenergy and produces products with a stable quality.

The technical solution for achieving the first object of this inventionrelates to the composition for the desulfurizer, characterized in thatsaid composition comprises three species of iron oxides which areferroferric oxide in the form of cubic crystalline phase (Fe₃O₄),amorphous ferric oxide (Fe₂O₃) and amorphous ferric oxide monohydrate(Fe₂O₃.H₂O), wherein the contents of the iron oxides in said are: 3.0 wt% to 3.5 wt % of Fe₃O₄, 28 wt % to 30 wt % of Fe₂O₃, 60 wt % to 62 wt %of Fe₂O₃.H₂O, the balancing being water and residual by-products of thisreaction, the above percentages are based on the total weight of saidcompositions. Said residual reactants of this reaction are theby-products remained during preparing said three kinds of iron oxides.

Said composition for the desulfurizer has a surfur capacity of at least40%.

The technical solution for achieving the second object of this inventionrelates to a process for preparing the composition for a desulfurizerwith a high sulfur capacity, characterized in that it comprises thefollowing steps: (1) mixing a solid ferrous compound with a solidhydroxide at a molar ratio of iron to hydroxyl in the range from 1:2 to1:3; (2) kneading the mixture feeds obtained in step (1) and making themreact completely; (3) drying the products obtained in step (2) in theair; (4) washing and filtering the feeds obtained in step (3); and (5)naturally drying or baking the solids obtained in step (4) to form acomposition for a desulfurizer with a high sulfur capacity.

In the above preparation process, the solid ferrous compound in step (1)is selected from ferrous sulfate, ferrous nitrate or ferrous chloride,preferably the ferrous sulfate, and the solid hydroxide is selected fromsodium hydroxide, potassium hydroxide or calcium hydroxide, preferablysodium hydroxide. In step (2), the mixture is placed in a kneader, andthe reaction is sufficiently completed under the pressure of thekneader. The kneading time for the completion of the reaction is atleast 15 minutes, preferably 15 minutes to 30 minutes. When usingnatural drying in step (5), said compositon is placed in the air atambient temperature of 5° C. to 45° C., while using baking process instep (5), baking temperature is at most 90° C., preferably 70° C. to 90°C.

The advantageous effects of the present invention are as follows: (1)the composition for the desulfurizer comprises not only ferroferricoxide in the form of cubic crystalline phase, but also two kinds ofamorphous ferric oxides including amorphous ferric oxide and amorphousferric oxide monohydrate. Thus, the desulfurizing performance of saidiron oxides with various structure can be fully utilized. The determinedcontent of iron in the desulfurizer guarantees a stable quality of thedesulfurizer products containing the ferric oxides. (2) According to theprocess of the present invention, the various ferric oxide products canbe acquired through one-off appending the solid ferrous compound andsolid hydroxid as the feed stocks, and the process is so simple as tooperate. (3) According to the process for making a composition for adesulfurizer with a high sulfur capacity of the present invention, solidferrous compound and solid hydroxide are reacted at a given ratio in thesolid phase. Compared with liquid phase precipitation process generallyused at present, it is easier to operate and easier to control thereaction products, without colloidal ferrous hydroxide Fe(OH)₂ andferric hydroxide Fe(OH)₃ formed during the reaction process, so avoidingthe trouble of filtrating these colloids. (4) In the present invention,the reaction for preparing three kinds of iron oxides is an exothermicone, the heat released is sufficiently used in the mixing and thekneading process, so it consumes less energy. (5) Dehydration of ironoxide hydrate formed in the solid phase reaction and crystalline phaseconvertion of different iron oxides are completed by drying in the air,which is simple and less energy consuming as that the composition forthe desulfurizer is kept stable, and further the stability ofdesulfurizing performance is guaranteed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the X-ray diffraction Pattern of a composition for adesulfurizer with a high sulfur capacity.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will be described in detail in conjuction with but notlimited to the following drawing and specific examples.

FIG. 1 represents the X-ray diffraction Pattern of the composition forthe desulfurizer with a high sulfur capacity, compared with the standardX-ray diffraction fiche (J.C.P.D.S fiche), wherein d values are equal to2.9636, 2.5265 and 2.0940, said data represent the cubic crystallinephase of ferroferric oxide (Fe₃O₄).

The main raw materials are solid ferrous sulfate and sodium hydroxide inexamples, said materials are eligible industrial products, whereinferrous sulfate contains 88 wt % to 93 wt % fraction of ferrous sulfatewith heptahydrate (FeSO₄.7H₂O), and sodium hydroxide contains 90 wt % to93 wt % fraction of NaOH. Tap water is used for washing. Baking isoperated in a electric-hot blast drying box. The type of the kneader isCD4×ITS multifunctional catalyst molding machine.

EXAMPLE 1 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

The preparation process in this example includes the following steps:

(1) homogeneously mixing 32 kg ferrous sulfate powder with 12 kg sodiumhydroxide at a molar ratio of iron to hydroxyl being 1:2.8,

(2) placing the mixture feeds obtained in step (1) in a kneader andkneading them for 3 hours to complete the solid phase reaction,

(3) drying the reaction products obtained in step (2) in the air,

(4) adding water to the mixture obtained in step (3) and stirring,repeatedly washing said mixture until sulfate ion is absent in thefiltrate (which is usually examined with the barium chloride), thencentrifugally filtrating the mixture solution with a centrifuge,

(5) drying the solid obtained in step (4) at a temperature of 80° C. for3 hours, then obtaining the composition for the desulfurizer with a highsulfur capacity, labeling said composition as Composition A.

The Composition A comprises 3.3 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 29.0 wt % amorphous ferric oxide(Fe₂O₃) and 60.7 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

EXAMPLE 2 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

The preparation process in this example includes the following steps:

(1) homogeneously mixing 64 kg ferrous sulfate powder with 21.2 kgsodium hydroxide at a molar ratio of iron to hydroxyl being 1:2.4,

(2) placing the mixture feeds obtained in step (1) in a kneader andkneading them for 0.5 hour to complete the solid phase reaction,

(3) drying the reaction products obtained in step (2) in the air,

(4) adding water to the mixture obtained in step (3) and stirring,repeatedly washing said mixture until sulfate ion is absent in thefiltrate (which is usually examined with the barium chloride), thencentrifugally filtrating the mixture solution with a centrifuge,

(5) naturally drying the solid obtained in step (4) in the air to obtainthe composition for the desulfurizer with a high sulfur capacity,labeling said composition as Composition B.

The Composition B comprises 3.3 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.9 wt % amorphous ferric oxide(Fe₂O₃) and 61.9 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

EXAMPLE 3 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

In the present example, the steps are same as example 2, except that thekneading time in step (2) is 1 hour. Said composition for thedesulfurizer with a high sulfur capacity is labeled Composition C.

The Composition C comprises 3.2 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.7 wt % amorphous ferric oxide(Fe₂O₃) and 61.8 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition. composition is labelledas Composition E.

The Composition E comprises 3.1 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.6 wt % amorphous ferric oxide(Fe₂O₃) and 61.2 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

EXAMPLE 6 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

In the present example, the steps are same as example 5, except that thedrying in step (5) is naturally drying in the air. Said composition islabeled as Composition F.

The Composition F comprises 3.0 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.7 wt % amorphous ferric oxide(Fe₂O₃) and 61.3 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

EXAMPLE 7 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

The preparation process in this example includes the following steps:

(1) homogeneously mixing 64 kg ferrous sulfate powder with 20 kg sodiumhydroxide at a molar ratio of iron to hydroxyl being 1:2.3,

(2) placing the mixture feeds obtained in step (1) in a kneader andkneading them for 1 hour to complete the solid phase reaction,

(3) drying the reaction products obtained in step (2) in the air,

(4) adding water to the mixture obtained in step (3) and stirring,repeatedly washing said mixture until sulfate ion is absent in thefiltrate (which is usually examined with the barium chloride), thencentrifugally filtrating the mixture solution with a centrifuge,

(5) drying the solid obtained in step (4) at 70° C. for 3 hours toobtain the composition for the desulfurizer with a high sulfur capacity,labeling said composition as Composition G.

The Composition G comprises 3.2 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.6 wt % amorphous ferric oxide(Fe₂O₃) and 61.6 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

EXAMPLE 8 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

The preparation process in this example includes the following steps:

(1) homogeneously mixing 92 kg ferrous sulfate powder with 28 kg sodiumhydroxide at a molar ratio of iron to hydroxyl being 1:2.2,

(2) placing the mixture feeds obtained in step (1) in a kneader andkneading them for 1 hour to complete the solid phase reaction,

(3) drying the reaction products obtained in step (2) in the air,

(4) adding water to the mixture obtained in step (3) and stirring,repeatedly washing said mixture until sulfate ion is absent in thefiltrate (which is usually examined with barium chloride), thencentrifugally filtrating the mixture solution with a centrifuge,

(5) naturally drying the solid obtained in step (4) in the air to obtainthe composition for the desulfurizer with a high sulfur capacity,labeling said composition as Composition H.

The Composition H comprises 3.2 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.6 wt % amorphous ferric oxide(Fe₂O₃) and 61.5 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages are

EXAMPLE 4 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

The preparation process in this example includes the following steps:

(1) homogeneously mixing 64 kg ferrous sulfate powder with 22 kg sodiumhydroxide at a molar ratio of iron to hydroxyl being 1:2.5,

(2) placing the mixture feeds obtained in the step (1) in a kneader andkneading them for 15 minutes to complete the solid phase reaction,

(3) drying the reaction products obtained in step (2) in the air,

(4) adding water to the mixture obtained in step (3) and stirring,repeatedly washing said mixture until sulfate ion is absent in thefiltrate (which is usually examined with barium chloride), thencentrifugally filtrating the mixture solution with a centrifuge,

(5) drying the solid obtained in step (4) at a temperature of 90° C. for3 hours to obtain the composition for the desulfurizer with a highsulfur capacity, and labeling said composition as Composition D.

The Composition D comprises 3.3 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 29.0 wt % amorphous ferric oxide(Fe₂O₃) and 62.0 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

EXAMPLE 5 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

In the present example, the steps are same as example 2, except that thekneading time in step (2) is 2 hours, and the drying in step (5) isbaking at a temperature of 90° C. for 1 hour. Said based on the totalweight of said composition.

EXAMPLE 9 The Composition for the Desulfurizer with a High SulfurCapacity and the Process for Preparing the Same

The preparation process in this example includes the following steps:

(1) homogeneously mixing 64 kg ferrous sulfate powder with 18.4 kgsodium hydroxide at a molar ratio of iron to hydroxyl being 1:2.1,

(2) placing the mixture feeds obtained in step (1) in a kneader andkneading them for 0.5 hour to complete the solid phase reaction,

(3) drying the reaction products obtained in step (2) in the air,

(4) adding water to the mixture obtained in step (3) and stirring,repeatedly washing said mixture until sulfate ion is absent in thefiltrate (which is usually examined with barium chloride), thencentrifugally filtrating the mixture solution with a centrifuge,

(5) drying the solid obtained in step (4) at 80° C. for 2 hours toobtain the composition for the desulfurizer with a high sulfur capacity,labeling said composition as Composition I.

The Composition I comprises 3.3 wt % ferroferric oxide in the form ofcubic crystalline phase (Fe₃O₄), 28.9 wt % amorphous ferric oxide(Fe₂O₃) and 61.8 wt % amorphous ferric oxide monohydrate (Fe₂O₃.H₂O),and the balancing being sodium sulfate and water. The percentages arebased on the total weight of said composition.

The method for analyzing various iron oxide contents in the compositionfor the desulfurizer with high sulfur capacity A to I is as follows:According to <<The chemistry analysis process for the iron ore and thecapacity process for measuring the amount of the whole iron withtitanium trichloride and potassium dichromate>> (GB 6730.5-86), thewhole-iron content and ferrous ion content of the composition for thedesulfurizer can be measured, so as to figure out the total content offerric ion. Based on Thermogravimetry—Differential Thermal Analysispattern, the content of crystalline water in ferric oxidemonohydrate(Fe₂O₃.H₂O) can be obtained. From said content of ferrousion, the content of the crystalline phase of ferroferric oxide can becalculated, and the content of ferric ion of crystalline phaseferroferric oxide can be obtained accordingly. From the content ofcrystalline water in ferric oxide monohydrate (Fe₂O₃.H₂O), the contentof ferric oxide monohydrate (Fe₂O₃.H₂O) can be figured out, and thencontent of ferric ion of ferric oxide monohydrate (Fe₂O₃.H₂O) can beobtained. The content of the ferric ion in ferric oxide (Fe₂O₃) can befigured out by subtracting the content of ferric ion in ferroferricoxide and in ferric oxide monohydrate (Fe₂O₃.H₂O) from the total contentof ferric ion.

Evaluation of the performance of the composition for the desulfurizerwith a high sulfur capacity in the present invention.

Detailed Examination Method

At normal temperature (ambient temperature, usually 5□ to 45□, the samein the following paragraphs) and pressure (atmosphere pressure, usuallyone atmosphere pressure, the same in the following paragraphs), 5 gComposition A to I prepared in example 1 to example 9 were evaluated byusing a standard gas containing 40000 ppm hydrogen sulfide (H₂S). Forqualitative detection, the sulfur from the outlet is measured by using1% self-prepared silver nitrate solution, and for quantitativedetection, the WK-2C integrated microcoulombmeter (manufactured byjiangsu electroanalysis instrument factory) was used. The lowestdetectable content of said instrument is 0.2 ppm. The test results areshown in table 1.

TABLE 1 Example 1 2 3 4 5 6 7 8 9 Composition A B C D E F G H I Sulfurcapacity (%) 48.0 50.8 47.2 51.3 51.0 40.0 50.2 46.9 47.9

It can be seen from table 1 that the composition for the desulfurizerwith a high sulfur capacity of the present invention when used under atnormal temperature and pressure, has a sulfur capacity of at least 40%,and up to 51.3%.

Results of application experimental test using desulfurizers preparedfrom the composition of the present invention are as follows.

APPLICATION EXAMPLE 1

135 g Composition I in example 9 was mixed with 10 g sheep-sweet-earthand 5 g graphite together, followed by adding a proper amount of water.The mixture was kneaded and extruded to form the desulfurizer in theshape of a bar with a diameter of 4 mm. Said desulfurizer has a sulfurcapacity for breakthrough of 41.0% and a intensity of side pressure of49N/cm.

APPLICATION EXAMPLE 2

135 g Composition B of example 2 was mixed with 10 g sheep-sweet-earthand 5 g graphite together, followed by adding a proper amount of water.The mixture was kneaded and extruded to form the desulfurizer in theshape of a bar with a diameter of 4 mm. Said desulfurizer has a sulfurcapacity for breakthrough of 43.0% and a intensity of side pressure of52N/cm.

1. A compositions for a desulfurizer with a high sulfur capacity,characterized in that said composition comprises three kinds of ironoxides which are ferroferric oxide in the form of cubic crystallinephase (Fe₃O₄), amorphous ferric oxide (Fe₂O₃) and amorphous ferric oxidemonohydrate (Fe₂O₃.H₂O), wherein the contents of the iron oxides in saidare: 3.0 wt % to 3.5 wt % of Fe₃O₄, 28 wt % to 30 wt % of Fe₂O₃, 60 wt %to 62 wt % of Fe₂O₃.H₂O, the balancing being water and residualby-products of this reaction, the above percentages are based on thetotal weight of said compositions.
 2. The compositions for adesulfurizer with a high sulfur capacity according to claim 1,characterized in that the composition has a sulfur capacity of at least40%.
 3. A process for preparing the composition for a desulfurizer witha high sulfur capacity according to claim 1, characterized in that itcomprises the following steps: (1) mixing a solid ferrous compound witha solid hydroxide at a molar ratio of iron to hydroxyl in the range from1:2 to 1:3; (2) kneading the mixture feeds obtained in step (1) andmaking them react completely; (3) drying the products obtained in step(2) in the air; (4) washing and filtering the feeds obtained in step(3); and (5) naturally drying or baking the solids obtained in step (4)to form a composition for a desulfurizer with a high sulfur capacity. 4.The process for preparing the composition according to claim 3,characterized in that said solid ferrous compound in step (1) isselected from ferrous sulfate (FeSO₄), ferrous nitrate (Fe(NO₃)₂) orferrous chloride (FeCl₂), and said solid hydroxide is selected fromsodium hydroxide (NaOH), potassium hydroxide (KOH) or calcium hydroxide(Ca(OH)₂).
 5. The process for preparing the composition according toclaim 4, characterized in that said solid ferrous compound is ferroussulfate (FeSO₄), and said solid hydroxide is sodium hydroxide (NaOH). 6.The process for preparing the composition according to claim 3,characterized in that said kneading in step (2) is accomplished with akneader, and the kneading time for the completion of the reaction is atleast 15 minutes.
 7. The process for preparing the active componentsbased on claim 6, characterized in that said kneading is accomplishedwith a kneader, and the kneading time for the completion of the reactionis in the range from 15 minutes to 30 minutes.
 8. The process forpreparing the composition according to claim 3, characterized in thatthe drying in step (5) is naturally drying at a temperature of between5° C. and 45° C .
 9. The process for preparing the composition accordingto claim 3, characterized in that the drying in step (5) is baking, andthe baking temperature is at most 90° C.
 10. The process for preparingthe composition according to claim 9, characterized in that the bakingtemperature in step (5) is between 70° C. and 90° C.